Super Soaker Central

I don't know if there's another thread like this, so sorry if it's already posted.

Okay, so I'm doing a science project on launchers and I'm comparing throwing, slinshots, and air pressure. Obviously air pressure is the winner, but I want an excuse to try this out.

I'll post a blueprint later. I'm thinking of using some 3" PVC pipe for a barrel, some bungee cord, wooden dowels, and the lower receiver of the Nerf Fast Action Rifle (it's a homemade). Would this work?

I've considered this as well but never did anything about it. The focus is on constructing a good crossbow more than it is on building a WBL, though obviously the design has to be adapted for launching water balloons.

A well designed crossbow would seem to be able to launch balloons fairly decent distances. No idea how far though, and a traditional 3-man launcher would probably perform much better.

Well using bungee would make it a slingshot. For a true crossbow you have to have the power coming from a bow. Wood is the usual material, though I've seen bodged crossbows using skis. Leaf springs would be overkill for a WBL.

It would be interesting to see how a sling does. They can get ranges far greater than an unaided throw, but accuracy takes a lot of practice.

I would just use the bow arms commonly found on Nerf homemades. They are cheap, and you can get very good performance out of them. I have been working on making one shoot water, but a WB seems like it might be easier.

One major issue with water balloons versus arrows or Nerf/foam arrows is the sheer weight of the balloon. Even small balloons are 20x to 30x heavier than comparable foam arrows. Real arrows are a comparable weight to a small water balloon, but their shape is much better for flight through air (obviously ). You'll need fairly strong bungie cords if they are small and won't be stretched too far since you want a more mobile device. Might get ok ranges, but may be a good challenge to ensure the mechanism doesn't end up ripping itself apart.

Are you guys thinking of using direct propulsion or pneumatics? Direct would be easier, and that is what I would be using.

I haven't seen crossbows that use pneumatic plungers, unless you count spring powered as crossbows. However, I don't think springs could supply enough power; you'd need a bungee it seems. (That's what I assumed was meant by "crossbow"; a bow that uses a bungie, not a spring or spring&plunger.)

I thought you were building nerf-style crossbows. I have built small spring powered crossbows using 1" PVC and a clothespin trigger. it all depends on how big a spring you use, but with a relatively weak spring, my best one was capable of shooting random objects through cardboard boxes.
With a 2" bore and a bigger spring (I am thinking at least a k26) I have no doubt that I could throw a WB a good distance.

Okay! I got the blueprint done. Tell me what you think.

Off Topic: Is it spelled bungie or bungee?

Bungie is the name of the video game developer (famous for creating the Marathon and Halo franchises), "bungee" is the flexible cord.

I tried a bow-like launcher myself before, using a 3" pipe, two steel L brackets, a smaller PVC stick, and some exercise stretching band that seems to be similar to surgical tubing. The designed failed miserably, launching balloons no further than squirt gun range. If you get plenty of force and use a long bow, it may work considerably better. However, wood seems very prone to snapping; PVC would probably be better.

Okay so instead of wooden dowels I'll use PVC. What's the recommended length for cord and the "bow" part?

CPVC is much more bendy then PVC

You might not want to use PVC, because of the shatter factor, but that might just be my superstition. CPVC should be avoided because it is bendy. Less tension, less power. I would go with a nice length of yew, and shape it as needed.

Hmm... Yew. Isn't that what real bows are made of? It's not supposed to be lethal!

It won't be lethal. The only thing I was worrying about was the PVC shattering, so if you replace the really long arms of PVC with much shorter arms made out of yew, you would get the same power in a more compact form.